


so show me family

by shadowdance



Category: Fire Emblem: Fuukasetsugetsu | Fire Emblem: Three Houses
Genre: Alternate Universe - Modern Setting, Gen, Humor, Minor cursing, Prerelease, au where sothis is byleth's little sister
Language: English
Status: Completed
Published: 2019-07-01
Updated: 2019-07-01
Packaged: 2020-06-02 10:46:10
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,069
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/19439869
Author URL: https://archiveofourown.org/users/shadowdance/pseuds/shadowdance
Summary: ("Didn't you say you wanted a sibling?")In which Byleth finds himself with a new little sister.





	so show me family

**Author's Note:**

> This was a crack au where I told my friend "au where Jeralt takes in Sothis and she becomes Byleth's bratty little sister." I did not intend to actually write and post it, but here we are. Things might be a little ooc since this is prerelease.
> 
> Title is from "Ho Hey" by the Lumineers

Jeralt walks in the room with a little girl.

She doesn’t look any older than ten years old, tops; Byleth easily towers over her. One tiny hand is curled in Jeralt’s. Her green hair is a mess, tumbling lightly over her shoulders; a little golden headband shoves bangs out of her face. Her dress is long and tattered, eyes wide and green. She looks a little curious—not frightened, though.

Byleth says, “Who the fuck is that?”

Jeralt glares at him. “ _Don’t swear_ ,” he says through gritted teeth, and Byleth almost laughs. Jeralt has never cared before, after all. “This is Sothis.”

_Sothis_. She looks up at Byleth with wide eyes, and her mouth breaks into a tentative smile. He frowns. “And why is she here?”

“She’s your new sister,” Jeralt says cheerfully.

Dead silence.

“What?” Byleth finally sputters out. His head is spinning, and Sothis is still staring at him innocently. Byleth absolutely doesn’t trust that. “When did you— _what_?”

Jeralt sighs. He drops Sothis’ hand, clamps his own on Byleth’s shoulder. “It’s fine. She’s a lovely—”

“You cannot just go picking random kids off the streets and saying they’re _yours_ , Dad.”

“That’s not what happened,” Jeralt says defensively. He glances at Sothis, and Byleth follows his gaze. The little girl still gazes at them with wide eyes, so Jeralt drops his voice. “She has no home, and she liked the idea of having an older brother. Didn’t you say you wanted a sibling?”

Byleth closes his eyes. “When I was like, four.”

Jeralt sighs. He rakes his fingers through his hair, and it strikes Byleth how _old_ his father is. He’s always seen his father as an unmovable mountain, someone with grand heroism and wisdom. But now Byleth is almost as tall as him, and he can see the lines crossing Jeralt’s face, the exhaustion permanently etched in his features. This has to be hard on him, too.

“Alright,” Byleth says reluctantly. “Whatever.”

Jeralt smiles. He ruffles Byleth’s hair, just like when Byleth was a kid. “Good boy,” he says, voice low. “Be nice to her, okay?”

He squeezes Byleth’s shoulder and walks off, hands in his pockets. Byleth grinds his teeth—how very _Jeralt_ to dump the kid on him. But it’s not like it matters, anyway.

He glances at the little girl, who’s still staring at him curiously. She reminds him of a baby bird, almost, and the thought wipes away most of the discomfort. He tries to rearrange his face out of a frown.

“Hi,” he says uncomfortably. “I’m Byleth. You’re…my new sister?”

Sothis gazes up at him. She has to tilt her head up to meet his gaze, and it’s kind of cute, if Byleth is honest. She _is_ pretty adorable—a tiny stance, poofy hair, sweet gaze.

But then her mouth slips into a mischievous smile. “I believe so,” she says cheerfully, voice louder than Byleth expected. “Why does your hair look like burnt Panini?”

Any sort of affection Byleth might have felt vanishes. He glares; Sothis laughs. It’s a childish laugh. He hates it.

“Nice to meet you, Big Brother.”

+

Byleth goes into his father’s room that night. Jeralt is shaving, inspecting himself in the mirror; when he sees Byleth in the reflection, he smiles.

“Remember when I first shaved my beard? You wouldn’t look at me without bursting into tears for two days.”

Byleth’s jaw hardens. “Where did you get Sothis?”

Jeralt’s grin fades. He turns the sink off, a steady _drip drip drip_ filling the silence. Byleth sighs, sags his shoulders.

“I didn’t mean it like that,” he says. “I’ll…be fine around her. But I want to know who my new sister is.”

Jeralt doesn’t respond for a long time. The faucet is still dripping, the water splashing against the drain. Byleth wonders, in that long silence, if there’s something he’s intruding on.

“She’ll tell you,” Jeralt says, neatly stepping around the question like Byleth is a kid again. It irritates him. “Eventually. In her own time.”

Byleth lowers his gaze. Jeralt turns back to the mirror.

“Go to bed, Byleth. It’s been a long day for everyone.”

Byleth shrugs. He wants to ask more, but there’s a final note to Jeralt’s voice, the one Byleth has heard since he was a child; _don’t ask for more than what you know._ So he leaves the room quietly.

(Throughout the night, he hears Sothis’ snores rip through the walls, keep him awake. He has never wanted to murder a child more.)

+

Jeralt makes Byleth take Sothis with him to school.

“Why,” Byleth huffs out. Sothis is clinging to Jeralt’s side again, dressed in a dark blue dress. She smiles at Byleth; he frowns back.

Jeralt shrugs. “Because I can’t bring kids to my job, and she can’t be left alone by herself. She’s _ten_. Do you remember what you did when you were ten?”

Byleth scowls. “We don’t talk about it.”

“Exactly.” Jeralt ruffles Sothis’ hair, and she beams at him. She looks like a little angel, all smiles and innocence. Byleth doesn’t trust that.

“But I’m not good with kids,” he argues.

Jeralt rolls his eyes. “You’re a teacher. Your job is _working_ with kids.”

Byleth doesn’t have a good response.

“I’ll lose her,” he says, as a last excuse, and Jeralt laughs.

“Oh, c’mon. I lost you in a supermarket when you were six. Children don’t wander very far.”

_You’re assuming I would go looking for her_ , Byleth thinks scathingly, but then Sothis lets go of Jeralt’s leg. She flits to Byleth’s side and smiles shyly at him; it would make any person’s heart melt. She really _is_ adorable. And the truth is, Byleth knows he won’t ever refuse his father.

“If I have to bring her with me, I want the leash backpack,” he says flatly. Sothis’ jaw drops, but Jeralt merely shrugs.

Which is how Byleth ends up walking a little kid to school.

“I cannot _believe_ you,” Sothis complains. Her cheeks swell when she pouts, and she keeps dragging her feet on the ground. The backpack is a little tarnished now, but it still does its job well. Byleth has his fingers wound tightly around the leash; all he can see is the back of a slightly tattered monkey, smiling at him mischievously. It kind of reminds him of Sothis. 

“I don’t want you running off and hurting yourself,” Byleth snaps, and Sothis stops. She looks at him, practically beaming.

“Aw, you do care for me!”

Byleth grinds his teeth. “No, Dad would just kill me.”

“You care,” Sothis says cheekily. “You don’t have to pretend.”

Byleth briefly considers dropping the leash and letting her run in traffic, but to be honest, she’s actually being obedient. So far, she hasn’t pulled on the backpack, nor has he had to quicken his pace. He actually looks more like he’s walking a dog, which is extremely stupid. A lot of people have given Byleth weird looks, and he’s not sure if it’s because of the leash, or because he and Sothis look nothing alike.

“How did Dad even find you, anyway?” Byleth asks. He just wants to know—but Sothis stops dead in her tracks. Her shoulders are small, but Byleth immediately sees the tension rise in them, sees a little bit of light escape her soul.

“It doesn’t matter. He’ll tell you, won’t he?”

Byleth thinks about the heavy lines around Jeralt’s face again, the way he said the same words last night. He doesn’t respond.

A bird flutters past. Sothis’ gaze traces its movements, and then she skips lightly. “Come on,” she calls out. “You’re going to be late.”

“You don’t even know when my first class starts.”

She shrugs and skips ahead, careful not to strain on the leash. Byleth glares at her back, and then discreetly checks his watch.

9:56. Four minutes until class starts. But it’s not like he’s going to let Sothis know that she’s right, so he grits his teeth and quickens his pace.

+

Byleth doesn’t mind his students. They can be unruly, sure, but they’re also pretty smart. Claude von Riegan likes to pretend he’s not, but Byleth has looked at his tests before, and the truth is, there’s not much to correct.

But even his students can’t contain their curiosity when they see a little girl sitting in a corner of the classroom. Claude shoots Byleth a quizzical look; Byleth shrugs.

“Did everyone do the homewo—”

“Teach,” Leonie interrupts. She crosses her arms, glances at the little kid. “Who the hell is that?”

Byleth grinds his teeth. “Don’t swear,” he says, his voice so eerily reminiscent of Jeralt’s that Sothis looks up. She grins at him, and he nods curtly back. “That’s my sister.” (Sothis makes a face: _that?_ )

Ignatz’s eyes grow wide. “You have a sister, Professor? I didn’t know!”

“Neither did I,” Byleth grumbles.

Marianne sets her books down, and then moves almost shyly towards Sothis. She crouches down to her height, cocks her head to the side. “Aw, you’re so cute,” she coos, and Sothis beams her innocent-angel smile at her. “What’s your name?”

“Sothis,” Sothis says cheerfully. Byleth resists the urge to roll his eyes, but Marianne merely smiles sweetly. It’s rare for her—Byleth knows Marianne is the most mature out of all the students, but she usually keeps to herself, stays so quiet that neither a word nor a smile crosses her lips.

“That’s a wonderful name,” she says kindly, and Sothis beams at her. She sneaks Byleth a sly grin, brimming with chaos and mischief, one that Marianne misses. Byleth groans.

“Sit _down_ , Marianne,” he says sternly, and she stands up, shooting Sothis a sweet smile before flouncing back to her seat. Next to her, Lysithea has her arms crossed, staring at Sothis with what looks like distaste. She glances at Byleth, and her mouth twists in a mischievous smile. It’s so eerily similar of Sothis that a shiver ripples through Byleth’s shoulders.

This lesson is going to be _hell._

+

“Make me a sandwich.”

Byleth glances at the little girl perched on his armrest. She blinks at him with wide, owlish eyes, trying to look angelic as can be. Byleth still sees the dirt stains on her dress, though, sees the tattered monkey backpack hanging on the wall.

“What?” Byleth asks harshly. Sothis sighs.

“I’m hungry. Jeralt isn’t home. Can you make me a sandwich?”

“I am not your _maid_ ,” Byleth huffs. Sothis’ face twists into a pout, eyes going wide and cheeks swelling and bottom lip trembling and _dammit,_ Byleth can never resist that stupid look. He sighs, throws down his book, and heads towards the kitchen.

“You should learn how to make your own food,” Byleth mutters. Then, “What kind?”

Sothis shrugs. She drops into a chair, kicking her legs absentmindedly. “Whatever. I’m just hungry.”

Byleth glares at her. She sticks her tongue out at him.

They don’t talk for awhile, not while Byleth looks for peanut butter in every cabinet—where the hell did Jeralt _put_ everything—and tries to make a decent sandwich. Of course this is much harder than it has to be. With Sothis, everything is.

Out of nowhere, though, she blurts out, “Did you know your mom?”

Byleth freezes. A big glob of peanut butter drips on the sandwich; he doesn’t notice. “Pardon?”

Sothis looks sorry she asks it, but she’s still a kid; she has no filter. She says, hesitantly, “Jeralt said…your mother died when you were young. Did you ever know her?”

Byleth’s grip tightens on the knife. He wants to say, _shut up_ or _we’re not going to talk about it._ There’s a small soft part of him that aches a little, something that wonders about his mother. Jeralt never talks about her, so Byleth doesn’t, either. He’s told himself he doesn’t want to, and he’s always believed it.

But he surprises himself by saying, “I have a few memories of her. She was nice.” He doesn’t know where this comes from. Sothis hums, and wrings her tiny hands together.

“I didn’t know my mother,” she says simply. “I still don’t, not really.”

This is an increasingly solemn subject for a ten-year-old girl. Yet Byleth sees the cant of her shoulders rise a little, sees a little gloom leave her gaze.

“I’m sorry,” he replies softly. He doesn’t quite know how she feels, but he knows their feelings overlap somewhat. Sothis nods and smiles—not mischievously, though. A real smile, something softer and lighter, genuine.

“Thanks,” she says, and Byleth sets the sandwich in front of her. Immediately, her smile vanishes.

“I don’t like white bread.”

Byleth groans, any warm feelings he had towards her quickly disappearing. “You are so annoying,” he complains, but he gets up anyway, already searching for the wheat bread.

+

Lysithea doesn’t quite grasp a concept that Hanneman is teaching, so Byleth sets up a tutoring session with her. Unfortunately, he cannot leave Sothis at home, so he ends up dragging her to the session with her. It went well last time, he figures. Sure, Lysithea didn’t look happy, but she wasn’t unruly or anything. But then again, Marianne was there.

“You brought _her_?” Lysithea eyes Sothis reproachfully, like she’s an animal that might attack. Sothis frowns at her, stamping her foot. Byleth places a hand on Sothis’ shoulder.

“Look, she’s fine. She’ll sit in the corner and just listen,” he explains.

“Don’t count on it,” Sothis mutters under her breath. Byleth squeezes her shoulder—harder than necessary.

Lysithea still doesn’t look convinced, but she opens her notebook anyway. Most of it is notes, although there are some questionable scribbles in the margins that Byleth chooses not to ask about. That’s just Lysithea—diligent in class, but carries some sort of wildness inside of her, something that can’t be contained.

Sothis, for her part, listens most of the time. But when there’s a pause—Byleth has to take out his own book, they’re switching subjects, something like that—she makes a disgruntled noise. Lysithea shoots her sharp glares, and Byleth _really_ regrets bringing Sothis now. But he tries to direct Lysithea’s attention away, tries to ignore Sothis growing more restless in the corner.

Until Sothis asks, “What do you draw in your notebooks?”

Lysithea snaps her head up, eyes widening. “Excuse me?”

“ _Sothis_ ,” Byleth hisses, but Sothis ignores him. She stands up, strides to Lysithea’s side.

“These,” she says, pointing to the black scribbles Byleth has tried to ignore. “What are those? It looks like you wrote something, and then crossed it out.”

To Byleth’s astonishment, Lysithea blushes. He’s never seen her look embarrassed before. “It’s not important!”

Sothis squints. “Was it something embarrassing? Like, did you write down the name of your crush or something?”

Lysithea’s jaw drops, and then clenches furiously. Byleth presses a hand against his forehead, feels the throbbing of a headache come on.

“Sothis—”

“Ignatz has been teaching me to draw," Lysithea interrupts. Her cheeks are bright red. "So I practice in my notebook. But Hilda says they're not ladylike, so I cross them out."

Sothis blinks. “What do you draw?”

“Sothis,” Byleth repeats. They both ignore him.

“Well, that one was a pegasus eating someone,” Lysithea explains, prodding her finger on one dark scribble. “It was supposed to look like Lorenz, but Marianne told me to scribble it out. And then _that_ one”—she points to another one, scribbled just above some notes on a math formula—“was Claude with his hair on fire.”

Sothis’ eyes go round. “Really? That’s cool! Can you draw a dragon? That’d be really cool.” 

Lysithea stares at her. One, two, three seconds pass. Then she bursts into laughter.

“Why not,” she says, and Byleth slouches in his seat, giving up. Apparently, everyone has forgotten this is a tutoring session. He watches Sothis bend excitedly over Lysithea’s notebook, and fights the urge to roll his eyes.

Thank gods he’s getting paid for this shit.

+

Sothis makes Byleth braid her hair.

He’s not good at it. Her hair is long and tangled, and his fingers snag on too many knots. Sothis snaps, “Watch it!” and he yanks on her hair before trying again.

“Why are you having me do this, and not Dad?”

“Because I always wanted an older sibling to do it for me,” Sothis says sweetly, and Byleth rolls his eyes. He pulls sharply on Sothis’ hair, and she squeals.

“Stop that! Or I’m going to hit you with a book!” she scolds. Byleth sighs.

“Have you always wanted an older sibling?”

In the mirror, he sees Sothis suddenly go quiet, mischief falling away like a mask. She always looks so much older when she doesn’t look playful, and that shocks Byleth more than anything else. “Maybe,” she says uncertainly. “Did you? Ever want a sibling, I mean.”

Byleth hasn’t thought about this in a long time. He shrugs, discomfort crawling up his spine. “I don’t know. I wanted to be less lonely sometimes.”

Sothis nods vigorously, hair bouncing. Byleth grits his teeth and tries to grab her hair carefully. “Me, too,” she says. “I was tired of being alone. I’m glad your dad took me in.”

Byleth frowns. He is still burning with a lot of questions—apart from the mother talk, he still doesn’t know much about Sothis, how she came to them. She’s an enigmatic, but she won’t give up parts of her past. Then again, he supposes that’s the attitude he tries to emulate sometimes.

Maybe they are more similar than what meets the eye.

Byleth accidentally brushes over a knot again. Sothis shrieks. “That hurts!”

Byleth rolls his eyes again. “Oh, my apologies. It’s not like I’m doing it on purpose.”

“With you, I never know,” Sothis grumbles. Then she sits up straighter. “Hey, Byleth, I meant to ask—is there someone you like?”

Byleth drops the hairbrush, a flush working up his neck. “What?”

“Oh, you know,” Sothis says, waving her hand in the air dismissively. “You’re, what, twenty-one? Almost twenty-two? Isn’t there anyone who has caught your eye?”

Byleth hates how his cheeks are flooded with color, hates how hot he feels. There isn’t anyone, too, which is stupid. “I’m the youngest teacher there, Sothis.”

Sothis taps her chin thoughtfully. “And you have no friends you like? Oh, wait. You don’t have any friends.”

Byleth yanks on her hair; she hisses, and then laughs, clapping her hands together. “But seriously. I’m sad you don’t like someone.”

“Why?” Byleth sets the brush down, starts fiddling with Sothis’ hair. Out of the corner of his eye, he sees her face grow serious again.

“Because you’ve been lonely for awhile, right? I think you deserve someone who makes you feel less alone.”

Byleth doesn’t know how to respond to that. He blinks in the mirror, taking in the answer. Sothis smiles kindly at him—and then wriggles in her seat.

“Also, I wish I could tease you, but I can’t.”

“Oh, you do that anyway,” Byleth grumbles. “I heard you tell Dad that I’ve made some pretty bad life choices so far. Starting with my hair.”

Sothis laughs, the sound light and pretty. “But am I wrong?”

Byleth grits his teeth. He tugs on her hair, and she yelps. “Shut up or I won’t do these stupid braids.”

In the end, the braids he does are messy, uneven, but Sothis doesn’t care. She shrieks in delight, clasping her hands together and twirling around. Without warning, she flings her arms around Byleth’s waist; he stiffens in surprise, but she lets go quickly.

“I love it, thank you!” she beams at him, and then races down the hallway, shouting Jeralt’s name, looking for him. Byleth sits in her room and stares at himself in the mirror; against all odds, he sees his mouth slope upwards in the smallest smile.

+

Rhea is there, when Byleth arrives home from school. Sothis is still wearing the monkey backpack, but she stops dead in her tracks when she sees Rhea.

“Hello,” Rhea says. She looks very serene, sitting at the kitchen table, in a long white dress. Her long green hair sweeps past her shoulders, an elegant headband framing her face. Every time she comes, Byleth always feels like he’s not _worthy_ to be in her presence, like he’s rugged and dirty and inadequate. Like he’s a slug, basically, and Rhea is a butterfly on a flower.

“Hi,” Byleth says. He nudges Sothis, but the girl doesn’t move. Her eyes are slightly narrowed, and any trace of mischief or excitement is missing—she looks _upset_. Byleth hasn’t ever seen her look like this.

Then Sothis snaps out of it. She nods curtly at Rhea, and then drops the monkey backpack at Byleth’s feet. Without warning, she takes off down the hallway, and Byleth hears a door slam. Rhea bites her lip.

“I figured that would happen,” she sighs, and Jeralt shrugs.

“She’s a kid. You were the closest thing to a mother to her. Give it time.”

_Mother?_ Something tightens in Byleth’s stomach. He wants to ask more, but Jeralt almost seems to read his mind; his gaze connects with Byleth’s.

“Can you go check on her?”

Which is how Byleth ends up in front of a ten-year-old girl’s closed door, and realizes he doesn’t know how to properly go in. She’s upset, so should he just barge in, or knock, or—

The door swings open. Sothis tilts her head up at him.

“You could’ve just come in,” she says flatly. “I would’ve done that to you.”

Byleth rolls his eyes, but he follows her in the room. She drapes herself dramatically on her bed; Byleth hesitates, and then sits at the foot of it.

“You know Rhea, huh?”

Sothis heaves out a sigh, one bigger than her own body. “She was the one who sent me to Jeralt.”

Oh.

Sothis pushes herself up, meets Byleth’s gaze. She looks wiser beyond her years now, tired and worn thin. “She’s very nice,” she explains. “She took care of me. But…I think she knows stuff about my parents, and she wouldn’t tell me anything. And I kept asking. I kinda wonder if that’s how I ended up with you guys—because I wouldn’t stop asking questions.” She shrugs. “She said she’d be in contact, but I don’t really want to see her. Not unless she wants to tell me about my parents.”

Sympathy and guilt folds itself tightly in Byleth’s chest. He shifts closer to the little girl. He doesn’t really know what to say—comforting people has never been his strongest suit.

“Dad doesn’t tell me anything about Mom,” he confesses. “I think it’s too hard for him. So I have to make up my own vision of her, sometimes. I think she was really sweet, really kind. She had a nice smile.”

Sothis is watching him intently, eyes like a hawk. Sweat beads down Byleth’s neck. 

“I don’t really know Rhea,” he admits. “She’s…she’s very nice, but I don’t know her. Dad does. They’re kind of close. But...I can never tell what she’s thinking. I know she doesn’t...she doesn’t hate you. Maybe she thought we could take care of you better.” He hesitates, and then adds, “Either way, I’m glad you ended up with us.”

He has no idea what he’s actually saying, and he’s going on totally unrelated tangents, but it doesn’t matter. Sothis breaks into a tiny grin at the last sentence. “Really?”

Byleth shrugs. “Yeah. I mean—you’re less lonely now, right? You’re too young to be lonely, you know.”

She blinks at him. Her smile widens, and she laughs. “Has anyone said you’re a pretty good older brother?”

Byleth ruffles her hair. “Nah,” he says. “Never really was one until now.”

Sothis sits up straight. “Am I a good little sister?”

“No. You’re a gremlin.”

Her jaw drops, smile instantly vanishing. She points to the door. “I take it back! You suck! Get out!”

Byleth rolls his eyes, but he gets up. When his hand closes on the doorknob, he glances back at her, and a smirk breaks across his face. “For what it’s worth, though, I’d rather have you than any other gremlin.”

Sothis’ face flushes, either with anger or embarrassment. She grabs a book, raising it threateningly at him. “You really suck!”

Byleth shuts the door before the book can hit his face.

**Author's Note:**

> Yes, the monkey backpack was originally Byleth's.


End file.
